Research Interests

I study the atmosphere and ocean, focusing on geophysical fluid dynamics, climate change, and numerical modelling. On the GFD/climate side, I am interested in how waves, turbulence, and jets are generated and how they will respond to climate change. On the modelling side, I am interested in improving simulations by designing better time-stepping methods and developing stochastic representations of subgrid-scale features.

These are challenging scientific problems with important societal implications. I tackle them using computer simulations (with everything from conceptual toy models to general circulation models) and laboratory experiments.

Some recent highlights from my research group are listed below, with links to published papers.

• Turbulence
  • Aircraft turbulence will increase in response to climate change, including severe turbulence globally.

  • Severe clear-air turbulence has already increased by 55% since 1979.

  • A new method for forecasting clear-air turbulence has been proposed and tested.

  • A new sensor has been developed for measuring atmospheric turbulence.

  • Eastbound transatlantic flights encounter more turbulence than westbound flights.

  • Multi-diagnostic multi-model ensemble forecasts of clear-air turbulence are superior to deterministic forecasts.

• Jet streams
  • The jet stream is 15% more sheared since 1979, an expected consequence of climate change.

  • The upper-level jet stream will strengthen and modify transatlantic flight times.

  • Zonal jets have been studied in laboratory experiments and numerical simulations.

• Waves
  • Loss of balance and instabilities can generate strong gravity waves.

  • Gravity waves can impact the large-scale flow by inducing regime transitions.

  • The atmosphere adjusts to solar eclipses by emitting gravity waves.

• Fuel-optimised flight routes
  • Flight routes are often inefficient and create unnecessary emissions.

  • This remains true even if the assumption of constant aircraft weight is relaxed.

  • Allowing en-route airspeed variations creates even further potential for emissions savings.

• Time stepping
  • The RAW filter I developed for the leapfrog scheme is accurate and works in semi-implicit models.

  • Weather forecasts are improved by the RAW filter and its variants.

  • The RAW-filtered leapfrog scheme performs as well as RK3 in benchmark experiments, at substantially less computational cost.

• Stochastic modelling
  • Stochastic parameterization of ocean eddies improves climate simulations.

  • Stochastic parameterization represents a new view of weather and climate models.

  • Stochastic fluctuations in air–sea fluxes modify climate simulations.

  • Stochastic noise may induce sudden stratospheric warmings.

  • I explored stochastic modelling in a review article and two special issues.

• Climate change
  • Climate change is affecting take-off conditions for aircraft.

  • I discovered a new climate feedback from the hydrological cycle.

  • The water cycle and ocean salinity play important roles in climate.

  • I discussed rapid climate change in a review article.

• Quasi-geostrophic theory
  • Quasi-geostrophic theory performs well even outside its formal limits.

  • I led the development of QUAGMIRE, a quasi-geostrophic numerical model of the rotating annulus.

• Science and art
  • Weather has been depicted extensively in classical music and pop music.